Your answer depends on the nature of your MIL's assets and the authority, if any, that your SIL's acted under. The POA gives you (or your wife), the right to act on your MIL's behalf. You basically "step into her shoes." If the assets in question were jointly owned with your SIL, then they would have had the right to close the accounts. There may be little you can do about that. If the assets were in your MIL's name alone, then they would appear to have acted improperly and you should be able to retrieve the assets.
Whether this was done properly or not, your SILs' intentions matter. If they are planning on setting the funds aside and using them for your MIL's care, then that is one thing. If they are planning on spending the money on themselves, that is completely different.
This could be a legal matter, but it does not need to be. It could be more of a family matter. Rather than get upset with your SIL for doing something they probably should not have, the FIRST step would be to have a family meeting and decide what happens NOW. If you can come to an agreement, you will have preserved the family relationships. If you cannot do so, then you should contact a lawyer to determine how best to proceed.
James Frederick
