Ethics Pledges and Other Executive Branch Appointee Restrictions Since 1993: Historical Perspective, Current Practices, and Options for Change [Updated February 23, 2021] [open pdf - 1MB]
From the Summary: "On January 20, 2021, President Joe Biden issued Executive Order (E.O.) 13989 on ethics. E.O. 13989 created an ethics pledge for executive branch appointees and provided for the administration and enforcement of the pledge. President Biden's executive order shares some features with previous executive order ethics pledges issued by Presidents Donald Trump, Barack Obama, and Bill Clinton. [...] This report begins with an overview of the relationship between the public and the executive branch, including the use of laws, executive orders, and other guidance and Administration policy to regulate interactions. A brief summary of recent executive orders is then provided, including a side-by-side analysis of ethics pledges from the Clinton, Obama, Trump, and Biden Administrations (see Appendix). This analysis is followed by observations about the similarities and differences among the four pledges."
CRS Report for Congress, R44974
Congressional Research Service: https://crsreports.congress.gov/