The following responses were gathered from offices of Legal Authorities:

Usurpation and forcible acquisition of the property of non-Muslims in non-Muslim countries is not permissible, if they are not at war with Muslims. And even if they are at war with Muslims it is still better that Muslims not do that.[1]

The written reply of Hazrat Grand Ayatollah Fazel Lankerani's (May Allah increase his life) office:

There is no problem if the Kufar (non-believers) are at war with the Muslims, and if they are not at war then it is not permissible, and during a time of peace the possessions of non-Muslims are respectable.

The written reply of Hazrat Grand Ayatollah Behjat's (May Allah increase his life) office:

It is not permissible as their property is considered respectable during a time of peace. Only during a time of war with the specific permission or public notice from an Islamic judge would this be permissible.