Handbook: House Marik indicates on page 13 that the Treaty of Terra formalized relations between the Hegemony and the Free Worlds League after James McKenna removed the Alliance regime, and indicates that both parties gained through having secure borders. The timeline on page 17 puts the date for the Treaty of Terra being signed as 2316.
The map of the borders between the Terran Hegemony and Free Worlds League visible on the map on page 13 showing the Lyran Commonwealth founding in 2341 shows Wyatt, Chertan, Bordon, Connaught and Van Diemen IV as being Terran Hegemony worlds. The map on page 17 of Handbook: House Liao dated 2366 shows all 5 as being Free Worlds League worlds. Lastly, the map on page 24 of Handbook: House Marik of the Terran Hegemony/Free Worlds League border as at the end of the Age of War in 2571 shows all 5 worlds as being back in the Terran Hegemony.
The timeline in Handbook: House Marik doesn't indicate any kind of war between the Hegemony and the League during this period (or at all), and the Star League Sourcebook indicates that McKenna's campaigns don't appear to have been focussed in the direction of the Free Worlds League. Is the border shown on the 2341 map in Handbook: House Steiner correct? House Marik (The Free Worlds League) mentions that when the Treaty of Terra was signed, McKenna assured the Free Worlds League received reassurance that it's space would not be violated by the Hegemony, and that McKenna instead went on to "liberate" worlds from the Dieron Federation while trading peacefully with the League, which would suggest that if the border did move back and forth within that period, it wasn't as a result of warfare.