At first glance it may not seem that either of these denominations take this principal seriously in their practice. However, on look to the Heidelberg Catechism as it discusses the second commandment and you find the following:
Q & A 96
Q. What is God's will for us
in the second commandment?
A. That we in no way make any image of God
nor worship him in any other way
than he has commanded in his Word.
Notice the second part of this explanation of this commandment says that we should not worship God, "in any other way that he has commanded in his Word." That would mean that the official understanding of our standards is not that of, everything is permissible as long as God has not prohibited it, but rather, we can and should only do the things God commanded be done in worship. We officially believe the scriptures teach the regulative principle. I am still on the fence if I totally agree with the regulative principle, but I do find I am leaning more and more in that direction.
That leads to my questions. First, how did two denominations that both believed in the regulative principle seem to abandon it and add things like advent wreaths? Second, what do those who read thing about the permissibility of advent wreaths based on the teaching of scripture. I know some of you simply like them, my question is not one of like of dislike, but are we wrong based on what the Bible teaches us to use them in worship?
EDIT December 9, 2006
For more information and discussion on this topic see here and here at Challies Dot Com.