Rav Shmuel Eliyahu, Chief Rabbi of Safed (Tzfat), issued a psak today that people should not buy lulavs for the upcoming holiday that were grown in Gaza. Rav Eliyahu said that this would be a "mitzva haba ba'aveira", and such a person would be giving his money to the wicked people of Gaza.

Rather, one should buy from the farmers of southern Israel and we must assist them by giving them our business and not give our business to the farmers of Gaza or their brethren who burn down the fields of the Jewish farmers in the south.

Rav Eliyahu added that it is prohibited to buy anything from them - even shoelaces. One cannot buy things from people who shoot rockets at Sderot, Ashqelon or Beer Sheva. One cannot buy things from the people who dig tunnels in order to abduct soldiers or attack kindergartens.

Rav Eliyahu called on other rabbonim to refuse to give kashrut certification on lulavs from Gaza.
source: Haredim10

I have no problem with this. The one question I have is a similar one to the one asked during shmitta - are our vegetables coming from Gaza, making this moot, or are we careful to ensure that we are not buying our cucumbers either from the terrorists? I am not asking rhetorically - I really don't know the answer as to where our cucumbers and other vegetables come from, but if we only make a big deal out of the big things but are not consistent with the daily little things, the whole thing is pointless.