I hereby make known that it is forbidden for any Jew whose forefathers stood at Mount Sinai and has a portion in the G-d of Israel and His Torah, to remain a member in the Nationalist Council, which has lifted up its hand against the Torah of Moses and desecrates the laws of the Torah brazenly. G-d forbid for any good Jew to be in their company, let alone to aid and abet these sinners in any way, shape or form.
And since the honourable [British Mandate] government has given permission to opt out of the Nationalist Council, it is a holy obligation upon all observant Jews to go as soon as possible and to opt out from the Nationalist Council while it is still possible. (Responsa Saba Kadisha 1:32)
When a certain Rebbe came to Eretz Yisroel and visited Rav Kook, and then later wanted to come visit Rabbi Alfandari, Rabbi Alfandari said, “I have had enough of Rebbes. Since he went there, let him not come here.” (Related by Rabbi Yitzchok Grohman, quoted in Mishkenos Haro’im v. 6)