Absolutely. This is a shadow phase action, so as long as you meet the requirements and costs for the action (in this case, a minion and 6 companions), you can play as many times as possible. Obviously the move limit cannot be reduced below 1, and any increases made after the shadow phase would allow you to keep moving
Two things:
1. When I was looking through the rulebook the other day after reading this post, I didn't find anything that said the move limit CAN'T be dropped below 1. Most cards specify that it can't, but this card doesn't need to do that, because it can only be used if you've already moved once anyway.
2. The section on modifiers says that anytime you drop below 0 as a result of modifiers, the final number is considered 0. However, it then goes on to say that each time a new modifier is added, ALL previous modifiers are recalculated. So if I made the move limit -10 during the Shadow phase using
Ruined Capitol, and then you made the move limit +1 in Regroup by playing
Last Throw, we'd recalculate all modifiers for move limit and find that you're still at -8.