But concerning the withholding of funds, there is no potential crime
here either. There is a process in place to sort out any disagreement
between Congress and the president on such a matter. Section 683 of the
Impoundment Control Act of 1974 states that “whenever the President
determines ... that such budget authority should be rescinded … [or]
reserved from obligation for such fiscal year, the President shall
transmit to both Houses of Congress a special message” to that effect
with an explanation. The Congress then has 45 calendar days to concur,
or the funds are to be “made available for obligation” and “may not be
proposed for rescission again.”
Although Section 684 calls for a special message if the
funds are to be deferred within the fiscal year, this special message
does not force Congress to concur.
The lack of a special message from Trump for either section
is not an impeachable offense. First, the president clearly had not
made a conclusive decision that he wanted to propose the funds should be
“rescinded” or “reserved from obligation.” Neither Trump nor his
Democratic critics disagree that he was awaiting further information
before deciding whether or not he wanted the funds conclusively
rescinded. All he had done as of this summer was to withhold the funds temporarily. Therefore, it would have been premature for Congress to receive a proposal from him to rescind the funds.
More here.