From The Federalist:

If the administration wants to go on the offense, it could take a few practical steps in the right direction. Adding more cartels to the list of transnational criminal organizations would allow us to squeeze them as much as possible financially. But it would not be enough, as Giovanni Falcone advises, to “follow the money.” The Insurrection Act, which the president has mentioned before, is another instrument that would be useful in this fight.
Because of the Posse Comitatus Act, our troops on the border operate in a passive, observe and report capacity. The Insurrection Act could remedy that problem. If it is “clearly lawful,” as University of Texas Law School professor Stephen I. Vladeck writes that it is, for the president to use the act in immigration matters, then surely that lawfulness extends to border security. “And although Congress in the Posse Comitatus Act of 1878 generally prohibited use of the federal military for domestic law enforcement,” Vladeck writes, “the Insurrection Act was always understood as the principal exception to that general rule.”