The trouble with letting them suffer and burn is the infection spreads - the Chicago has infection already spread to Milwaukee [ which wasn't in great shape to begin with ], and now is spreading to the suburbs in WI, overwhelming local police.
Kill it now before it multiplies further!!!
The President can clearly employ Federal troops to enforce U.S. Federal law (e.g. - immigration, civil rights under the 14th Amendment). Any judge who rules otherwise is simply wrong... see Article 2 Section 2 of the Constitution). A far different question arises when the issue is state or local crime.
When the local police are overwhelmed and cannot depend upon increasing their ranks by appealing to the local government, the standard response would be for them to appeal to the state governor for assistance (State Police/National Guard).
If a governor is unwilling to assist, then the voters have to make a decision as to whether to keep that person in office, or to elect someone else. A governor may appeal to the Federal government for assistance as well, but once again: should a state governor be unwilling to act, the problem will likely only get worse.
Our issues with crime have everything to do with bad values, broken families and a debased culture. To this extent, a U.S. President, no matter how well intentioned, is unlikely to succeed in solving the crime problem merely by Federalizing law enforcement (outside of D.C., which is by design a Federal district).
The appeals process will now lead to Federal District Court rulings, which in turn will be appealed to the U.S. Supreme Court, regardless of which way they turn out.
The Supreme Court would then need to rule upon whether the President has the power under Article 2 Section 2 (
"The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States") to unilaterally direct National Guard troops to enforce state crime laws where the state authorities are unwilling or unable to do so.