Are Xeloxi supposed to be Guarding Precursor Anomalies?

Trying to clear a Heavily Defended Precursor Anomaly with one of my fleets

Note the Xeloxi banner associated to the Precursor Fleet.  When I try to attack at range, a message pops up saying "you are not at war". 

Won't let me attack, since  we are not at war.  When I try to move on to the hex with my fleet to engage directly, I get a dialog that says Do you wish to declare war on the Xeloxi. 

Trying the direct approach below

 

 Are the Xeloxi supposed to be able to control Precursor Dreadnoughts?