All praise be to Allaah.
The basic principle with regard to clothes is that they are permissible, except those which Islam has definitely excluded, such as gold and silk for men, except in the case of scabies and the like. Wearing trousers is not something that is unique to the kuffaar, but wearing tight trousers which show the shape of the body, even the ‘awrah, is not permissible. Loose pants are permissible, unless the wearer intends to resemble those of the kuffaar who wear them. The same applies to wearing a suit and tie. These are not garments that are unique to the kuffaar, so they are permissible, unless the wearer intends to imitate them.
To sum up, the basic principle with regard to clothes is that they are permissible, unless there is shar’i evidence to show that they are not allowed, as stated above.
And Allaah is the Source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions.