Why might the state of israel not always be seen as ‘legitimate'? *?

The state of Israel not always be seen as ‘legitimate' because Some members of the United Nations still not recognizing Israel’s right of existence. It is majorly denied by Palestinian and Arabic groups and asking to deny and delegitimize Israel.

It is not recognized as a sovereign country by all members of the world. 

Being Israel was provided as a Jewish state under the conditions of World War II, some believe the land was not legitimately gained. Arabs in particular question the validity of the country and whether or not it has the right to exist at the expense of Palestinian land. The land has been contested as long as the country has existed because of it being created out of other sovereign peoples' land. 

Both countries had to aprove annexation.