I do not consume commercial carrion chickens and meat certified by SANHA or any of the other similar outfits.

Answer

What will you do if they serve pork or dog or donkey meat? Amr Bil Ma'roof Nahyi anil Munkar, i.e. to provide naseehat - to instruct with virtue, and to forbid from evil/sin is Waajib for all Muslims in different degrees in accordance with their knowledge and jurisdiction. It is not permissible to mingle and associate with people even if they are the closest relatives, when they indulge in sin. Aiding or facilitating sinful acts is a major crime. The one who assists in sin is in the same category as the one who commits the sin.

The proposal suggested by you is an indication of the desensitization of Imaan - desensitized to the evil that is being perpetrated in your presence. Such desensitization eliminates the natural Imaani inhibition to sin, fisq, fujoor and even kufr. When the Imaan of people has been neutralized by desensitization they move within the purview of Allah's La'nat (Curse) and Ghadhab (Wrath).

Your presence at the venue where Muslims are devouring haraam carrion is like the presence of a person at a place of gheebat. Even if you do not actively engage in gheebat, the Shariah classifies you also as one of those who are indulging in gheebat. It is haraam to sit in a gathering where gheebat takes place.

Rasulullah (Sallallahu alayhi wasallam) prohibiting even passive participation and indulgence in sin and evil said: "It is not lawful for a person who believes in Allah and the Last Day to sit at a maa-idah (cloth/ table) where liquor is served." From these exceptionally stern warnings, it should be understood that even passive sin has a direct detrimental effect on Imaan.

On the basis of the principles formulated from such Ahaadith and Qur'aanic Aayaat, it is haraam to eat with people whilst they are devouring the rijs of certified carrion chickens and carrion meat. Even if you do not consume the carrion, you will be considered to be among those who devour the haraam filth.

Therefore, if you have no clarity on the relative's / friend's meat / chicken sources, then explain to him the reason for declining his invitation. Do not be concerned with his annoyance. Allah Ta'ala orders us in the Qur'aan to fear only Him, not others, and not shadows. By mentioning the reason, you will be proffering naseehat, and discharging your obligation of Amr Bil Ma'roof.

Attending and abstaining from the chicken / meat dishes will be aiding the relative/friend in the perpetuation of haraam. You will be guilty of the double sin of abstention from naseehat and of passive consumption of carrion, whilst the relative / friend will be committing only one sin - the sin of devouring the carrion filth.

It is necessary that they be informed of their error.