May one enter someone else’s Sukkah without permission?[1]
Initially, one may not enter into another person’s Sukkah without permission [of the owner, or his wife[2]] even if he does not intend to steal it from him, if the person is currently in his Sukkah.[3] However, it is even initially permitted to enter his Sukkah while the owner [or family members] is not there [unless the Sukkah contains expensive items which the owner may be particular in that other people do not use without his permission[4]].[5] [Likewise, one may not enter the persons home without permission to use his Sukkah even if no one is there.[6]] Bedieved, if one dwelled in another’s Sukkah without permission while the owner is there, he nevertheless fulfills his obligation, [as explained above in D regarding one who stole property with a Sukkah].
[1] Admur 637:9; Rama 637:3; Taz 637:4; See Piskeiy Teshuvos 638:2
[2] M”B 637:9 in name of Bikurei Yaakov
May other family members give permission? Some Poskim rule that only the wife is valid to give permission and not other family members, such as the children, unless the father explicitly gave them permission to allow others to enter. [Aruch Hashulchan 637:5]
[3] The reason: As perhaps the owner is particular in this as he does not want his friend to see him eating or doing his other needs [in his Sukkah] without his permission. [Admur ibid]
[4] Kaf Hachaim 637:15; Piskeiy Teshuvos ibid
[5] The reason: As certainly the owner will not mind, as a person desires that a Mitzvah be done with his property if it does not incur him any monetary loss. [Admur ibid; 14:9; M”B 637:9]
[6] Piskeiy Teshuvos ibid footnote 3