My opinion is that the defending unit could Return fire, since the conditions of the last played Combat card trump the first played
• In case of contradiction, between the effects of two Combat cards played in succession, the second card trumps the effect of the first one.
I think generally Return fire would not necessarily negate the ability of Light Infantry to return to their originating hex, but I have some doubts around what would happen if the Light Infantry had to take a retreat flag result. If you consider the wording on the LIS card, the unit can remain in it's current (retreated?) hex providing it makes the morale check, or return to the originating hex.
