After President Donald Trump reluctantly signed a bill on Wednesday that makes it harder for him to lift sanctions on Russia, the White House issued a curious statement in his name, complaining that the new law includes “a number of clearly unconstitutional provisions.”

Specifically, the president complained about sections 253 and 257 of the legislation, which state that the United States “does not recognize territorial changes effected by force,” and will “never recognize the illegal annexation of Crimea by the Government of the Russian Federation or the separation of any portion of Ukrainian territory through the use of military force.”

Since those statements simply reiterate nine decades of U.S. policy about not recognizing borders changed by force — which has been in effect since the Hoover Administration and was restated by Vice President Mike Pence on Wednesday — Trump’s objection to it seems to indicate that he is open to negotiating new borders for Ukraine as part of his stated desire to “make a deal with Russia.” What, if anything, Trump would get from Russia, in exchange for lifting sanctions related to its occupation of Crimea and support for separatist rebels in the east, remains unclear.

In fact, the White House’s own explanation of the legal basis for Trump’s objection to those sections of the law includes a clue that the president might be willing to let Russia keep Crimea. The problem with sections 253 and 257, Trump says in the signing statement, is that “those provisions purport to displace the President’s exclusive constitutional authority to recognize foreign governments, including their territorial bounds, in conflict with the Supreme Court’s recent decision in Zivotofsky v. Kerry.”

To decode that, it is important to know that in the Zivotofsky case, decided in 2015, the Supreme Court ruled that Congress could not force the Obama Administration to accept Israel’s unilateral annexation of Jerusalem, which was seized by force in 1967. Every American presidents since Harry Truman has insisted that legal sovereignty over Jerusalem, which is claimed by both Israel and Palestine, can only be settled in final status negotiations.

The American parents of Menachem Zivotofsky, who was born in Jerusalem in 2002, had sued the State Department in 2003 to obtain a passport for their son which would state that his place of birth was in Israel, in accordance with a law passed by Congress that same year. President George W. Bush signed that bill just before Menachem was born, but issued a signing statement making it clear that he would not obey the law, arguing that it “impermissibly interferes with the president’s constitutional authority to conduct the nation’s foreign affairs.”

While Trump has so far maintained that official ambiguity over Jerusalem’s status by not acting on his campaign promise to move the U.S. Embassy there from Tel Aviv, the fact that he brought up that case in relation to a part of the sanctions law barring him from recognizing any change to Ukraine’s borders strongly suggests that he sees the sovereignty of Crimea a potential subject of negotiation with Russia.

In light of this clue as to Trump’s intentions, it is worth keeping in mind that just last week he suggested on Twitter that his attorney general, Jeff Sessions, should investigate “Ukrainian efforts to sabotage Trump campaign.”