President Donald Trump teased a veto before signing the massive $1.3 trillion omnibus spending bill on Thursday. He did so, at least in his telling, reluctantly and with plenty of grievances against Congress and Democrats about what was in the bill and what wasn’t.

Trump also proposed a few solutions to avoid this problem for future spending bills, one of which included Congress giving him the power of a line-item veto. That would let the head of the executive branch essentially take a red pen to legislators’ work, editing out the parts he doesn’t like.

“To prevent the omnibus situation from ever happening again,” Trump said, “I’m calling on Congress to give me a line-item veto for a government spending bills.”

There’s only one problem: Congress tried that before, and the Supreme Court ruled it unconstitutional. Presidents retain the veto power, of course, but it’s all or nothing — they can’t pick and choose which parts of the legislation they want to sign.

The Supreme Court declared the line-item veto unconstitutional almost 20 years ago. The challenge came during the Clinton administration, after the Congress passed the short-lived Line Item Veto Act of 1996, which gave the president the power to scratch certain items from spending and tax bills.

Congress supported the law as a way to cut back on waste and pork-barrel spending in an attempt to get the federal deficit under control — though, as the Washington Post reported in 1998, lawmakers’ enthusiasm “cooled” after Clinton started nixing some legislators’ favored projects. Clinton used the power 82 times on 11 laws, according to the New York Times.

The challenge to the line-item veto came from New York City and its health care and hospital workers, after the president struck down a tax break tied to Medicaid funding; and from Idaho potato farmers, who fought back after Clinton knocked off a beneficial provision in a tax bill.

The Supreme Court ruled 6 to 3, in Clinton v. City of New York, that the line-item veto was unconstitutional because it gave unilateral power to the president to amend the text of laws — which is the legislative branch’s, not the president’s, territory. Justice John Paul Stevens wrote the majority opinion, saying line-item vetoes are “the functional equivalent of partial repeals of acts of Congress.”

“There is no provision in the Constitution that authorizes the president to enact, to amend or to repeal statutes,” he added.

Basically, the Supreme Court said, it’s up to Congress to get rid of the wasteful spending themselves, and send the final product to the president for him to sign, or reject, in full. If they didn’t like this process, then they’d have to amend the Constitution.

The line-item veto has been something presidents have wanted apparently since at least Ulysses S. Grant, and many governors do have line-item veto power for appropriations bills in their states. Other presidents have tried to bring back the idea in some form since the Supreme Court’s 1998 decision.

Bush made an attempt in 2006, trying to re-write the law so Congress could override a line-item veto with a simple majority, rather than a two-thirds vote (which is needed to override a regular old presidential veto.) Obama considered asking in 2010. Both faced challenges, as Congress isn’t often eager to give up its spending power — even if it could tweak such a law to withstand a constitutional challenge.