{Customs which it is not lawful for us to receive, or to
observe, being Romans} (eth(8820)ha ouk estin h(886d)in paradechesthai
oude poiein R(936d)aiois ousin). Note the sharp contrast between
"being Jews" in verse  20  and "being Romans" here. This pose of
patriotism is all sound and fury. It is love of money that moves
these "masters" far more than zeal for Rome. As Roman citizens in
a colony they make full use of all their rights of protest.
Judaism was a _religio licita_ in the Roman empire, only they
were not allowed to make proselytes of the Romans themselves. No
Roman magistrate would pass on abstract theological questions
( 18:15 ), but only if a breach of the peace was made
(ektarassousin h(886d)(936e) t(886e) polin) or the formation of secret
sects and organizations. Evidently both of these last points are
involved by the charges of "unlawful customs" by the masters who
are silent about their real ground of grievance against Paul and
Silas. Ethos (kin to (8874)hos,  1Co 15:33 ) is from eth(935c), to
be accustomed or used to a thing. The Romans granted toleration
to conquered nations to follow their religious customs provided
they did not try to win the Romans. But the Jews had made great
headway to favour (the God-fearers) with increasing hatred also.
Emperor worship had in store grave peril for both Jews and
Christians. The Romans will care more for this than for the old
gods and goddesses. It will combine patriotism and piety.