There was some uproar after Washington independently issued his proclamation of neutrality in April 1793, declaring America's lack of favoritism toward either Britain or France in the new European war. Washington's good buddy Alexander Hamilton thought that the United States' former treaty deal with France had been voided by the French Revolution and the overthrow of the monarchy, so he supported Washington's decision.

Over the next few months, a series of essays by "Pacificus" were published in Federalist newspapers. It wasn't too hard to figure out they were written by Hamilton, given that they included some of his more private feelings about the U.S.-France relationship (source).

The goal of the essays was to defend the proclamation of neutrality, especially once "Helvidius" (a pseudonym for James Madison) started writing response essays against the proclamation.

The Pacificus-Helvidius debates were part of a tradition of politicians writing under these fake names (often Latin or Latin-sounding), going back and forth over whatever the big issue was, like the Novanglus and Massachusettensis essays in 1774 about American independence or the Publius vs. Brutus debates over the Constitution.

Think election debates, but in print and drawn out over months about one particular issue. Also, a lot more eloquent.

In the first of the series of Pacificus essays, Hamilton helpfully lays out why people are upset about Washington's proclamation:

The objections in question fall under [four] heads—

1. That the Proclamation was without authority
2. That it was contrary to our treaties with France
3. That it was contrary to the gratitude, which is due from this to that country; for the succours rendered us in our own Revolution.
4. That it was out of time & unnecessary. (Source)

Hamilton—sorry, Pacificus—reminds readers, though, that proclamations like Washington's are only meant to declare that the country "is in the condition of a Nation at Peace with the belligerent parties, and under no obligations of Treaty, to become an associate in the war with either of them" (source). That's what the proclamation is really all about. It doesn't mean that the United States will stop honoring treaties or negotiations—just the ones that threaten neutrality.

Pacificus then addresses the question of whether or not Washington had the authority to issue the proclamation. Well, he argues, of course the executive branch has the authority since a "correct and well informed mind will discern at once that it can belong neit(her) to the Legislative nor Judicial Department and of course must belong to the Executive" (source).

The legislative branch doesn't deal directly with foreign countries, and the judicial branch is only brought in when there's litigation. So, the power must lie with the executive branch.

Since the Constitution puts the power to make treaties with the executive branch and the president is the head of the executive branch, Washington did have the authority. Congress gets to declare war and peace, but that's not what's happening here:

While therefore the Legislature can alone declare war, can alone actually transfer the nation from a state of Peace to a state of War—it belongs to the "Executive Power," to do whatever else the laws of Nations cooperating with the Treaties of the Country enjoin, in the intercourse of the UStates with foreign Powers. (Source)

Really, Pacificus' argument comes down to his closing line: that the proclamation "only proclaims a fact with regard to the existing state of the Nation, informs the citizens of what the laws previously established require of them in that state, & warns them that these laws will be put in execution against the Infractors of them" (source).

In other words: calm down, everyone, he's not doing anything wrong here.