I heard it said that women can not serve in the army because they would violate the law of women wearing men’s clothing due to the fact that they would have to carry weapons, which are considered to be a part of men’s attire. Could you please elaborate on this law and on the restrictions on women to carry/use arms.

The reason that most religious women do not serve in the army is because of serious problems in maintaining modest behavior within the military framework- not because of the need to carry arms. A woman is not permitted halachically to carry arms as a standard article of military dress; when she needs them for safety, she is obligated to carry arms and to know how to use them (Shu"t Iggrot Moshe Orach Chayyim IV 75).