In a post worth reading in full, he knocks down some of the hysteria about this action:

Trump’s actions have been greeted with now-familiar claims that he is sparking a constitutional crisis or threatening the rule of law.

Considering just the substance of what Trump has done, these are large exaggerations. Everything Trump proposes to do purports to be grounded in congressional statutes and much of what he aims to do does not rely on emergency power. Trump is not relying solely on Article II executive power, and he is not invoking executive power to disregard a congressional statute. Moreover, the statutes in question expressly give Trump authority in the areas in which he claims them.

There will be questions—some of them hard, and without obvious answers—about whether Trump’s legal team has interpreted these congressional authorizations, and the conditions on their use, accurately. But abstracting away for a moment from the deeply divisive context in which Trump has asserted these authorities, the types of statutory claims he is making based on delegated power are nothingburgers from the perspective of executive branch practice, especially in the foreign relations context. The executive branch every day relies on vague or broad or dim delegations of authority, and courts usually uphold these actions. And as Trump himself stated many times, courts will ultimately sort out his claimed statutory authority in the wall context as well.

Nor is Trump’s claim of emergency power outlandish—at least by the standards of past presidential practice. Many charge that Trump is declaring an emergency when there is no emergency. But this begs all the relevant questions. The relevant statute on which Trump relies does not define the term “emergency.” Presidents have always—really, always—had discretion to decide if there’s an emergency. And presidents have often declared emergencies under circumstances short of necessity, to address a problem that does not rise to an “emergency” as defined in common parlance to mean “a serious, unexpected, and often dangerous situation requiring immediate action.”