Yes, and you can still use some of their ports for getting rid of attrition. It appears to be very easy to fix for a programmer.
I write "some" because strangely enough this is what happens in 1.07 11 may beta
1. Ports in provinces you besiege you will always be able to enter
2. Ports in provinces you do not besiege you will in some cases be able to enter, some not. I have not been able to conclude what distinguishes them from one another.
It is amazing that this bug has not been fixed long ago. The most simple change would be that as soon as you are at war with another nation the MA access between the two of you is instantly revoked. 100% realistic. A slightly more complex one would be to add a test for being at war in the MA-access module I assume exists and which is called upon when the question arises.
In my current GC I am in a BB phase of a WC (presently 1780) and I have MA with ENG, FRA and SPA among other. Well, during the truce between the BB rounds I put appropriately sized armies in all, repeat ALL, of their provinces. Then when the truce is ended and they DOW me my armies immediately start besieging or fighting. I have a support limit of 30-40k in almost every one of their provinces and they have mostly minimal fortresses. It is sick.
