When the latecomer stands up to complete his prayer, he is praying alone, so he should not let anyone pass in front of him
When the imam says the salaam and the latecomer stands up to make up what he missed of the prayer, then at this point he is in fact praying alone, and he should prevent anyone who wants to pass in front of him, because the Prophet (peace and blessings of Allaah be upon him) enjoined that. If some people do not prevent people from passing in front of them, it may be because they are unaware of the ruling, or because of a different interpretation, because they think that since they caught up with the congregation, after they start to pray separately from the imam they still come under the same ruling as those who are behind the imam. But it is essential for the latecomer to prevent the one who wants to pass in front of him, when he stands up to make up what he has missed. End quote.
Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him).