Long story short. I was the first author of a research manuscript submitted but rejected previously. I am the main contributor of all stages of the research from planning and research question to running the entire analysis, writing up the report and manuscript, and presentation. Since I left my previous job, someone took over. However, it is under the unspoken assumption that I am still the first author for the next journal submission. When I receive the slightly changed manuscript which is primarily based off of my original manuscript, I found out that I was pushed into the second author position. What are my options? I am going to confront with my previous team since the current first author only oversaw the research at high level and haven't written neither the first nor the second manuscript, I feel putting this person as first author is an offense of academic integrity and ethical standards. Do I have the authority to block all the publication of this manuscript if this is not resolved justly?

Long story short. I was the first author of a research manuscript submitted but rejected previously. I am the main contributor of all stages of the research from planning and research question to running the entire analysis, writing up the report and manuscript, and presentation. Since I left my previous job, someone took over. However, it was the unspoken assumption that I would be still the first author for the next journal submission. When I received the slightly changed manuscript which is primarily based off of my original manuscript, I found out that I was pushed into the second author position. What are my options? 

I am going to confront my previous team since the current first author only oversaw the research at high level and has not written neither the first nor the second manuscript. I feel putting this person as first author is an offense of academic integrity and ethical standards. Do I have the authority to block the publication of this manuscript if this is not resolved justly?