Responding to Thursday’s Supreme Court decision upholding the constitutionality of the Affordable Care Act, Congressional Republicans have scheduled a vote in the House to repeal the law and Mitt Romney pledged to undo the measure if he’s elected president in November. But unless the GOP wins a super majority in the Senate — a scenario no one thinks is plausible — it can do little more than weaken Obamacare’s regulations and defund some of its provisions. Here is why:

1) Romney has no authority to issue waivers. Romney has promised to expand a provision of the Affordable Care Act that allows states to opt out of certain sections of the law to permit states to ignore it entirely. But the executive branch and the Department of Health and Human Services (HHS) likely don’t have the authority to grant such broad waivers. According to the law, HHS (together with the IRS) have waiver authority, but only if the states meet very specific requirements. Neither have blanket waiver authority, which would have to come from Congress. Sen. Ron Wyden (D-OR) — the author of the waiver provision — has challenged Romney’s claims, saying, “Anybody who tries to move outside the standards of the bill — which is the coverage and costs and the like — well I’ll certainly fight that. But I think lots of other people will too.”

2) Congress can’t repeal the full law through reconciliation. Without the necessary 60 votes in the Senate for full repeal, Republicans are pledging to use a budget reconciliation bill to undo the ACA. But this process would only apply to the budget-related elements of the law and would thus leave many portions — including the mandate — intact. As health care expert Robert Laszewski put it, “Romney could end up creating a chaotic environment driven by enormous uncertainty over just which parts of the new health care law would be implemented–for consumers, health care providers, and insurers.”

3) Republicans have nothing to replace it with. David Frum explains that since the expansion of coverage provisions go into effect in 2014, Romney would have just one year to both repeal and replace the law. Republicans haven’t even coalesced around a single plan — and many in the party believe that the federal government should leave health care alone and want to leave the entire reform process to the states. Thus, “if replacement does not happen in the first 100 days, it won’t happen at all—that is, it won’t happen as a single measure, but rather will take the form of dozens of small incremental changes adopted episodically over the next 20 years.”

4) Americans support Obamacare’s provisions. While Americans may not like “Obamacare” — and the political process of passing it — they do support its major provisions and are likely to resist any effort by Republicans to take away their benefits. A recent Reuters/Ipsos poll found that while 56 percent of Americans oppose the law as a whole, 61 percent of respondents favored allowing young adults to stay on their parents’ insurance plans until age 26, 72 percent wish to maintain the requirement that companies with more than 50 workers provide health insurance for their employees, and 82 percent of respondents favored banning insurance companies from denying coverage to people with pre-existing conditions. As more benefits roll out in 2014, it will be increasingly difficult for Republicans to argue for their repeal.

WASHINGTON, D.C. — Businesses should be allowed to deny health insurance to cancer patients, according to a Republican senator, because “our nation was based on the foundation of freedom and limited government.”

Discussing health care outside the Supreme Court today, Sen. Ron Johnson (R-WI) told ThinkProgress that there “shouldn’t” be a law requiring businesses to cover employees who have cancer because that would “create an obligation” for others. “When you create a right for somebody,” Johnson said, “you create an obligation for somebody else, and then you’re taking away that person’s right.”

KEYES: I know Richard Murdock had said even though businesses should give people, for instance, with cancer, health coverage, they shouldn’t be legally required by the federal government.

JOHNSON: They shouldn’t. Listen, our rights are life, liberty, and the pursuit of happiness. And when we start expanding beyond that realm, when you create a right for somebody, you create an obligation for somebody else, and then you’re taking away that person’s right. And that maybe doesn’t seem all that great, but it’s just true. Our nation was based on the foundation of freedom and limited government.

Watch it:

Under Obamacare, health insurance companies cannot deny people health insurance because of a pre-existing condition like cancer. Johnson remains strongly opposed to the law.

Unfortunately, he is not the first person to suggest that businesses should be permitted to deny insurance to cancer patients. Last week, Indiana Republican Senate nominee Richard Mourdock similarly argued that employers should be allowed to deny coverage to cancer patients “if they want to keep their health care costs down.”

Steven Perlberg contributed to this report.

The Supreme Court has upheld the individual mandate in Obamacare, paving the way for full implementation of the law in the states and ensuring that millions of uninsured Americans haves access to affordable coverage. The court upheld the provision as a tax, but found that it does violate the Commerce Clause.

The Medicaid expansion is limited, but not invalidated, the court found. In short, it decided that if a state does not expand the Medicaid program, as required by the law, the federal government cannot withhold Medicaid funds.

In short, “the entire ACA is upheld, with the exception that the federal government’s power to terminate states’ Medicaid funds is narrowly read.”

Chief Justice John Roberts joined Justices Sonya Sotomayor, Stephen Breyer, Ruth Bader Ginsburg, and Elena Kagan in the 5 to 4 decision. Justice Anthony Kennedy — who was considered a swing vote on in the case — sided with the conservatives.